We are using the BMIRR laser microsurgery/ video LM component to determine the behavior of kinetochore-free "acentric" chromosome fragments, and "monocentric" chromosomes containing one kinetochore, created at various stages of mitosis in living plant endosperm. During metaphase acentric fragments and monocentric chromosomes were transported towards the closest spindle pole at a rate similar to that of anaphase chromosomes. By contrast, acentric fragments generated during anaphase moved to the spindle equator. This behavior, which is different from that of acentric chromosome fragments in animal cells, reveals that forces for poleward chromosome motion can be generated external to the kinetochore and suggest that the mechanism(s) positioning chromosomes differ between plants and animals. Abstracted to the 1995 ASCB meeting.